Returned amount of money in a feeling of hostility (6)
I believe the answer is:
animus
'feeling of hostility' is the definition.
(I've seen this before)
'returned amount of money in a' is the wordplay.
'returned' says the letters should be written in reverse.
'amount of money' becomes 'sum' ('sum' can be a synonym of 'amount of money').
'sum'+'in'+'a'='sumina'
'sumina' back-to-front is 'ANIMUS'.
(Other definitions for animus that I've seen before include "Ill-feeling; hatred" , "Deep-seated hostility or vital force" , "Hostile spirit in speech or action" , "Malicious ill-will" , "Hostility, ill-feeling" .)